My invisions used to take ages to change a lense when they were brand spankin' new.
Now they've been apart a few times to be cleaned they are much easier.
I've really given them some abuse pulling them apart and they have took it. the only thing to be careful of, is making sure you don't tear the foam on the inside of the frame.
When you put them back together, try using a little spit on the lugs, it helps them to slip back in!
Good goggles!
